The recent electronic devices such as cellular phones, micro video cameras, and portable information terminals use a connection base designated as a cradle (also referred to as a docking station) for sending and receiving data to and from desk top personal computers.
The cradle mounts a plug thereon and is connected with a cable via which the cradle and a desk top personal computer are connected to each other. On the other hand, electronic devices such as portable information terminals have a receptacle, and the receptacle provided on the electronic device can be connected with the plug provided on the cradle to secure high speed data transfer between the electronic device and the desk top personal computer. One of the simplest forms of the cradle is a charger for cellular phones.
Conventionally, this kind of cradle is unique to electronic devices connected with the cradle. However, highly versatile cradles equipped with a connector connectable with various kinds of connectors of cellular phones have been invented (Japanese Published Unexamined Patent Application No. H11-177670).
In the above-described invention, the cradle includes a holding rail for holding a cellular phone and a connector connected with a connector of the cellular phone. The connector of the cradle is held on the cradle in such a manner as to be movable up and down, back and forth and around via springs.
With this structure, even when there is a relative displacement between the connector of the cellular phone and the connector of the cradle, the connector of the cradle can freely move to be engaged with the connector of the cellular phone.
However, the provision of the above-described connector to the cradle increases the number of components of the cradle. It is simpler in structure to directly engage the receptacle connector provided on the electronic device with the plug connector provided on the cradle side.
The interface connector (or an I/O connector) mounted on such a cradle is generally a multi-polar dual in-line connector having two rows of contacts. In the dual in-line plug, the dual in-line contacts are surrounded by insulative fixed vertical walls protecting the contacts from being direct touched by a hand. Such a dual in-line plug is so-called four-wall shrouded, thereby having a large outer size.
However, electronic devices (micro video cameras, for example) to be connected with a cradle having a dual in-line plug are increasingly being reduced in size, which inevitably requires size reduction in a dual in-line receptacle provided for the above-described electronic devices. For this reason, it has been sought to miniaturize a dual in-line plug installed in the cradle, leaving almost no room for the formation of insulative fixed vertical walls surrounding the contacts (the so-called no wall header).
However, even if a dual in-line plug is miniaturized until there is no room left for insulative surrounding walls, when the contacts placed unprotected are subjected to dust or handling, it may become an indirect cause of a contact failure of the contacts. For this reason, dustproof measures have been sought for miniaturization of the dual in-line plug.
Furthermore, when security is taken into consideration, it is preferable to array dual in-line female contacts of fixed contacts in a dual in-line receptacle provided on an electronic device, and to array male contacts of flexible leaf springs in a dual in-line plug provided on a cradle, since the female contacts receive a contact pressure from the male contacts.
In other words, as compared with the fixed contacts which receive the contact pressure, the male contacts which give the contact pressure tend to be comparatively short-lived as a result of repeated insertion and removal of the connector. For this reason, it is not preferable to provide the short-lived male contacts to the connector mounted on the electronic device because it requires disassembling partially the electronic device in order to replace the connector.
Therefore, when the replacing the connector is taken into consideration, it is preferable to mount the dual in-line plug connector having male contacts of short-lived flexible leaf springs on the cradle. This holds true of cable connectors, without being limited to cradle connectors.
In order to solve the above-described problems, the present invention has an object of providing a miniature multi-polar electric plug which can prevent the contacts from being placed unprotected all the time.